Marin County 19-year-old's death is now attributed to serial killer Rodney Alcala.

For more than 35 years, former Marin County Sheriff's Det. Richard Keaton kept her photo at his desk.

A pretty blond girl at an Oakland A's game smiles at the camera lens through a halo of feathered hair, hand perched on her hip.

It's one of the last photos taken of 19-year-old Pamela Lambson alive. That day, authorities believe, she met a charming photographer who offered to help her launch a singing career.

Rodney James Alcala, a former contestant on "The Dating Game" and now a convicted serial killer, is believed to have traveled the country for nearly a decade in the 1970s, raping and killing women he first flattered with his camera.

For The Record Los Angeles Times Thursday, January 24, 2013 Home Edition Main News Part A Page 4 Local Desk 1 inches; 36 words Type of Material: Correction 1977 slaying: An article in the Jan. 20 California section about the 1977 slaying of Pamela Lambson, a possible victim of serial killer Rodney Alcala, misspelled the name of the San Francisco restaurant Scoma's as Skoma's. For The Record Los Angeles Times Sunday, January 27, 2013 Home Edition Main News Part A Page 4 Local Desk 1 inches; 36 words Type of Material: Correction 1977 slaying: An article in the Jan. 20 California section about the 1977 slaying of Pamela Lambson, a possible victim of serial killer Rodney Alcala, misspelled the name of the San Francisco restaurant Scoma's as Skoma's.

After three decades of trials, Alcala sits on death row for the murders of four women and a 12-year-old girl. Earlier this month, he got a life sentence with a minimum of 25 years for the New York murders of Ellen Hover and Cornelia Crilley.

But the full extent of Alcala's killing career may never be known. Authorities are circulating more than a hundred photos of women and children that were discovered in a Seattle storage locker Alcala used, and his recent convictions prompted authorities across the nation to reexamine old cases for connections.

Many of the investigations have fizzled, thwarted by degraded evidence and the fading memory of witnesses.

But Keaton and a team of detectives believe they've found Lambson's killer in Alcala. The only thing they need to file charges is a DNA match. But the samples from the case are too degraded.

The investigation was suspended last year, and the Lambson family will probably never see Alcala in court.

"There's no way to obtain justice," said Michael Lambson, Pamela's older brother. "How can you pay back all the lives taken?"

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Lambson was a bubbly, upbeat personality who always had a boyfriend, relatives remember. She trusted people easily and "could never believe that anyone would want to harm her," said her mother, Jean Lambson, 80.

The day in 1977 she was to meet the photographer, she donned a new white, flowing outfit. At an appointment with her stylist, Keaton said, she buzzed with excitement over what she thought was her big break and showed off the photographer's business card.

The next day, a jogger on a Mt. Tamalpais trail discovered Lambson's body, nude and battered, with her back against a tree. Six weeks later, authorities found her car at a private pier on Fisherman's Wharf, where multiple witnesses said Lambson had been arm in arm with a well-dressed, long-haired man with a camera. The car was parked "within eyeshot" of Skoma's Restaurant, which investigators were using as a base of operations, Keaton said.

It was around that time that Keaton grew obsessed with Lambson's case. Her family called for updates almost daily, and it still pains him how little he was able to tell them.

"Leads were coming in from all over the place, going nowhere," Keaton said. "It became personal."

But Keaton and his partner were forced to suspend their investigation after 18 months. During his career, many unsolved cases led him back to Mt. Tamalpais, where killers often dumped bodies. But he always remembered the mountain as the place where Pamela Lambson died.

When he retired in 1999, the case unsolved, he kept Lambson's photo with him -- pinned to a bulletin board in his home office, where he could see it from his desk.

"I just thought, someday we'll get an answer to this," Keaton said.

A break came with a phone call from his old employer. The Marin County Sheriff's Department reopened the case after Alcala wrote the department a letter asking for the date of Lambson's murder. Det. Ryan Petersen, who interviewed Alcala at San Quentin State Prison, said Alcala had read a news article that connected him to the killing and was trying to establish his innocence.

"He seemed like a guy who had many years to get good at telling people what they want to hear," Petersen said.

Keaton had thought Lambson's body was pushed from a car on a mountain road and tumbled to a stop in a seated position, arms and legs akimbo, her back against the tree.

But Damon Davis, a detective who pored over the evidence for six months, thought she had been posed. It was unlikely that her body had tumbled so far without striking other trees, coming to a rest in that position.

"That set off some bells and whistles in my head," Keaton said. "I knew that I was wrong."

Detectives determined that Alcala was the probable killer. They decided to inform the family of their new suspicions.

Jean Lambson got a call at her home in Utah. She answered the phone and began to tremble. The news hit like a "ton of bricks," she said.

The Lambsons say Alcala's fate is in God's hands. But the memory of the loss of their only daughter is still raw. For years after Pamela Lambson was killed, her mother would burst into tears at the kitchen sink, seized by sudden waves of grief, Michael Lambson recalls.